Prior packet transmission and switching systems were employed primarily to transmit data. In such systems, delay experienced by the packets was not a significant problem. Consequently, buffer memories having a large number of memory stages were used to smooth random packet load variations prior to transmission of the packets. This increased memory size causes packets to experience long delays through a packet network, if that network is busy, i.e., processing many packets. In packet transmission and switching systems that also transmit voice signals, any significant delay experienced by the individual packets is undesirable because it results in signal impairments that are annoying to the subscribers.
One possible solution to the delay problem is to use a so-called "shorter" packet buffer memory, i.e., one with fewer storage stages. Use of such a shorter buffer memory causes packet buffer memory overflow problems if the buffer is processing many packets which, in turn, cause loss of packets. Such loss of packets causes unwanted and annoying gaps in the reconstructed speech signal. Additionally, re-transmission of the lost packets is not feasible for speech signals because of the resulting delay incurred in re-transmission.
The packet buffer memory overflow problem may be avoided by reducing the packet transmission load on the system. This, however, is economically undesirable.